s8 (1)
A maintenance order in regard to the custody or guardianship of, or access to, a child, made in terms of this act, may at any time be rescinded or varied or, in the case of a maintenance order or an order with regard to access of a child, be suspended by a court if the court finds that there is sufficient reason therefor.

Although the Divorce Act is inclusive of maintenance and parenting plan amendments, it is important to remember that in South Africa these are two separate issues and must be felt with as such.
This section of the Divorce Act can be used in both situations when applying for variations.